Idling Problem

[600rob]

Hi folks,

ive had a 2002 1.0 yaris for a few months now and so far it seems to be okay, i have however noticed that when coming to a stop, (coming to a red traffic light for example) as you come off the gas the revs drop normally to idle. But after a second or two the revs then go up and down again several times before settling.

The revs don go up really high but the engine sounds almost like some one is applying and releasing the gas pedal. This doesnt happen every time i come to a stationary position but it seems to be getting more frequent.

sometimes the revving goes on for ages and only stops when i give it a fairly good rev after which it seems to settle and idle normally again.

On the flip side if the engine is idling normally and i just press and release the gas pedally a little it seems to cause the enginge to go into this cycle of revving up and down.

The problem only seems to be intermittent at the moment but it could become something worse.

anyone got any idea what it could be?

my initial thoughts were something to do with the intake of air into the engine.. possibly a split breather hose or something like that?

any other ideas or causes?

[600rob]

okay so im still trying to work this out as it is only an itermittent problem but seems to be occuring more frequently.

today with the bonnet open the car started doing the same thing but you could hear the distinct sound of air being sucked in just before the engine would rev. you can feel the air being pulled in at the mouth of the air intake and the sound is fairly loud, coming from the rear section of the airbox. so its almost certainly something to do with the air/breather system.

could it be right to assume that with each time there is a big induction of air as i described, the air fuel ratio is being upset which is causing the erratic up and down idling??

on inspection no visible splits of cracks in any of the components or any loose connections. still no one with any sugestions? Its not due a service for a while so id like to locate and sort it out myself rather than paying out.

[Madasafish]

Faullty Idle Control valve

OR

Air leaks in pipes around inatks to air filter

OR

http://www.toyotaownersclub.com/forums/index.php?app=forums&module=post&section=post&do=reply_post&f=49&t=125711

OR

MAF sensor needs cleaning

OR

EGR valve needs cleaning.

Is the Engine Management Light on?

Does it come on when you switch on the ignition? (If not it's possible bulb has blown or the last owner removed it to hide a problem)...

[pirks]

Got my car back today from the garage, it took them 6 days to find out the EGR valve needed cleaning (cars under warranty so i wont touch much of it until the warranty runs out in 3 months time)

The symtoms were the revs hunting at tickover with a cold engine and you could actually see this on the rev counter. car sounded like a bag of spanners to put it nicely and the mpg was down slightly also.

If yours sounds like the same problem then clean the EGR valve.

I also took a video of the revs rising and falling to show the dealer so he couldn't try and bu***hit me which he didn't do in the end anyway

[600rob]

thanks for the responses guys, madasfish,

The eml light does come on the goes out shortly after starting the engine up.

I'll have a good clean our up of the egr valve and maf sensor, might aswell clean the throttle body while im at it.

Can anyone recomend a suitable cleaner as ive read some posts which suggest certain types can damage the sensors and also the rubber seals leading to further problems.

I was going to use Wynns carburettor cleaner but i want to be sure its okay before i go and upset things even more

[Madasafish]

I use carburettor cleaner. No apparent problems.

(not used it on rubber.. check first )

[ChrisYar99]

I have a similar problem when idling in my '99 1.0 Yaris. This might sound like a silly question, but is it normal for the rev counter to drop all the way to nothing when idling? I've noticed it doing this, and although it may be my imagination, it seems like I need to give it a bit of petrol way too soon as I'm pulling it up to biting point. Also noticed that whenever I'm idling, the whole car shakes/vibrates (probably normal), but it does this inconsistently as if it's struggling to settle. I don't have any EML light on, although I constantly have a blue coolant warning light appearing when I first start up the car in the mornings. The car drives awfully until it warms up, basically feels like I'm engine braking when I change from first to second gear as I bring my foot off the clutch. Argh, problems!

[Madasafish]

I have a similar problem when idling in my '99 1.0 Yaris. This might sound like a silly question, but is it normal for the rev counter to drop all the way to nothing when idling? I've noticed it doing this, and although it may be my imagination, it seems like I need to give it a bit of petrol way too soon as I'm pulling it up to biting point. Also noticed that whenever I'm idling, the whole car shakes/vibrates (probably normal), but it does this inconsistently as if it's struggling to settle. I don't have any EML light on, although I constantly have a blue coolant warning light appearing when I first start up the car in the mornings. The car drives awfully until it warms up, basically feels like I'm engine braking when I change from first to second gear as I bring my foot off the clutch. Argh, problems!

Idle control valve?

see.. http://www.toyotaownersclub.com/forums/index.php?showtopic=109248